I've used GDB and here is the message: Program received signal SIGILL, Illegal instruction.0x00005555555e40b0 in _D3std8internal4math11biguintcore7BigUint3powFNaNbNfNkMSQCcQCbQBvQBtQBjmZQs ()
Here is the link to the source code: https://github.com/MuriloMir/Fermat-primality-test